PECULIARITIES OP^ MUSCLE TISSUE 



65 



CHAPTER V 

 PECULIARITIES OF MUSCLE TISSUE 



Extensibility and Elasticity of Muscle. — If a rubber band is suc- 

 cessively loaded with a number of small weights, it suffers an extension 

 each time. The height of these extensions remains the same through- 

 out this test and is proportional to the load applied. If the weights 

 are then removed one by one, the rubber band again shortens and 

 eventually assumes its original length. If a muscle, such as the 

 gastrocnemius, is successively extended by a limited number of weights 

 of 10 grams each, it is found that the extensions are greatest directly 

 after the application of the weight and then gradually decrease^ 



/ 



Fig. 35. — Extensibility and Elasticity. 

 A, rubber band and B, gastrocnemius muscle of frog successively loaded with 10 

 gram weights. The second curve shows a decreasing extension for equal increments, 

 hence, the line joining the end of the ordinates is curved. 



(Fig. 35B). But naturally, each weight must be permitted to act 

 for a moderate length of time, because the muscle substance is viscous 

 and yields only slowly to the strain. If the weights are now removed 

 one by one, the muscle again shortens, but does not attain its former 

 length. Its detension, therefore, is imperfect and hence, the excised 

 muscle must be regarded as being incompletely elastic. Its behavior 

 is similar to that of other organic bodies.^ While in its normal posi- 

 tion in the body, its elastic power is of course absolute, so long as it is 

 not acted upon by excessive weights. 



If the weights are added continuously, the elastic power of the 

 muscle is eventually overcome. Beginning at this point, its extension 

 occurs with great rapidity until it tears. In the case of the sartorius 

 muscle, this breaking point lies at 500 grams and in the case of the 

 gastrocnemius at about 750 grams. From these figures it may 

 readily be gathered that the strain which such small masses of muscle 



^ Dreser, Archiv fiir Exp. Path. u. Pharm., xxvii, 1890, 51. 

 2 Brodie, Jour, of Anat. and Physiol., xxix, 1895, 367; and Haycroft, Jour, of 

 Physiol., xxxi, 1904, 392. 

 5 



